Patch "crypto: aesni - handle zero length dst buffer" has been added to the 4.15-stable tree

This is a note to let you know that I've just added the patch titled

crypto: aesni - handle zero length dst buffer

to the 4.15-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
crypto-aesni-handle-zero-length-dst-buffer.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Stephan Mueller <[email protected]>
Date: Thu, 18 Jan 2018 20:41:09 +0100
Subject: crypto: aesni - handle zero length dst buffer

From: Stephan Mueller <[email protected]>

commit 9c674e1e2f9e24fa4392167efe343749008338e0 upstream.

GCM can be invoked with a zero destination buffer. This is possible if the AAD and the ciphertext have zero lengths and only the tag exists in the source buffer (i.e. a source buffer cannot be zero). In this case, the GCM cipher only performs the authentication and no decryption operation.

When the destination buffer has zero length, it is possible that no page is mapped to the SG pointing to the destination. In this case, sg_page(req->dst) is an invalid access. Therefore, page accesses should only be allowed if the req->dst->length is non-zero which is the indicator that a page must exist.

This fixes a crash that can be triggered by user space via AF_ALG.

---
 arch/x86/crypto/aesni-intel_glue.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

@@ -824,7 +824,7 @@ static int gcmaes_decrypt(struct aead_re
 	if (sg_is_last(req->src) &&
 	    (!PageHighMem(sg_page(req->src)) ||
 	    req->src->offset + req->src->length <= PAGE_SIZE) &&
-	    sg_is_last(req->dst) &&
+	    sg_is_last(req->dst) && req->dst->length &&
 	    (!PageHighMem(sg_page(req->dst)) ||
 	    req->dst->offset + req->dst->length <= PAGE_SIZE)) {
 		one_entry_in_sg = 1;

Patches currently in stable-queue which might be from [email protected] are

queue-4.15/crypto-af_alg-whitelist-mask-and-type.patch queue-4.15/crypto-aesni-handle-zero-length-dst-buffer.patch